The present invention relates to a bearing apparatus, and more particularly to a bearing apparatus including a split-type rolling bearing and a housing which supports the rolling bearing.
In an engine of such as an automobile or a marine vessel, a bearing for supporting a crankshaft which converts the reciprocating motion of a piston into rotational motion is disposed between adjacent counterweights or between a counterweight and a large end of a connecting rod, so that a split bearing which is circumferentially split in two halves is used.
Sliding bearings have conventionally been used as the aforementioned supporting bearings. However, since there has been an increasing demand for engines with less fuel consumption in recent years, the use of rolling bearings which are circumferentially split in place of the aforementioned sliding bearings has been proposed to reduce the rotational loss.
This split-type rolling bearing has, for example, a pair of split outer ring halves, a plurality of rollers disposed so as to be cable of rolling on the respective inner surfaces of the both split outer ring halves, and a pair of split cage halves for retaining the respective rollers so as to dispose them at substantially equal intervals in the circumferential direction. Further, a crankshaft is fitted in the rolling bearing as an inner ring member.
The aforementioned split outer ring halves can be obtained by fabricating a cylindrical outer ring from a bearing steel and subsequently by slitting that cylindrical outer ring into two halves. As a method of splitting the cylindrical outer ring into two halves, a method is known in which a notch for inducing a split is formed in a portion of the cylindrical outer ring, and the outer ring is split by applying an external force thereto by a press (e.g., refer to JP-A-7-317778).
However, with such a splitting method, in most cases a crack produced from the notch extends straightly along the axial direction. For this reason, in a case where a split roller bearing using the split outer ring halves obtained is incorporated in a portion to be used, there is a problem in that the pair of split outer ring halves are liable to be offset in the axial direction. If an offset occurs in the split outer ring halves, there is a possibility that noise and vibration can occur when the rollers roll in the vicinity of mating surfaces of the outer ring halves where this offset has occurred.
Accordingly, to suppress such an axial offset of the outer ring halves, a split outer ring half has been proposed at least a circumferential end of which has a concave-and-convex shape including a slope portion inclined with respect to a line extending along the axial direction and a slope portion inclined in the opposite direction to that of this slope portion (e.g., refer to JP-A-2005-337352). The split outer ring half in JP-A-2005-337352 is fabricated by cutting a hoop material made of a metallic material such as JIS Standard SCM 415 by a punching tool to obtain a blank material, by applying this blank material to a cylindrical receiving metal fitting, and by curving it into a substantially semicylindrical shape by using an appropriate bending tool. FIG. 8 shows an example of a split outer ring half 40 thus fabricated. If such split outer ring halves 40 are used, since the aforementioned concave-and-convex shapes mesh with each other at the mating surfaces, it is possible to prevent the pair of split outer ring halves from being axially offset. In addition, it is considered that even in a case where a radial offset has occurred at the mating surfaces and a radially stepped portion has occurred between circumferential end portions of the opposing split outer ring halves, since each roller obliquely hits against an edge 41a of a slope portion 41 and gradually rides over the stepped portion, thereby making it possible to alleviate the impact energy and suppress the noise and vibration.
However, although the rolling roller initially collides against an apex 42 of the projecting portion, the contact area between this apex 42 and the peripheral surface of the roller is smaller than the contact area between the peripheral surface of the roller and the edge 41a of the slope portion 41, so that the impact during the collision is large. For this reason, although the noise and vibration are alleviated as compared with a case where the roller rides over a stepped portion parallel to the axial direction, there has been a demand for further improvement.